Numerical Analysis of the Durability of Structural Elements Under Thermal Cyclic Loading

Abstract

The methodological aspects of assessing the service life of new equipment (elements of gas turbine engines), the operating modes of which lead to non-stationary thermomechanical loads, are considered. The associated thermoviscoplastic processes of deformation and damage states of the degradable continuum are modeled. A model of thermal fatigue in polycrystalline structural alloys for arbitrary complex deformation trajectories is described, consisting of relationships that determine cyclic thermoviscoplastic deformation; evolutionary equations for damage accumulation and strength criteria for damaged material. Kinetic equations take into account the effects of nonlinear damage accumulation, are based on the introduction of a scalar damage parameter, and are based on energy principles. The related formulation of the kinetic equations for damage accumulation under low-cycle fatigue and long-term strength describes the nonlinear nature of damage accumulation. The criterion for the strength of damaged material is the condition that the damage reaches a critical value. Using the developed original methodological, algorithmic and software that allows for end-to-end numerical modeling of thermal cyclic processes, the problem of assessing the thermal cyclic durability of models of elements and components of gas turbine engines during thermal pulsations has been solved. The results of an analysis of the influence of the angle of inclination of cooling channels in a model of combustion chamber pipes on the thermal cyclic durability are presented. The issues of the influence of complex thermal cyclic deformation, accumulation of fatigue damage, plastic deformations and creep deformations on the thermal fatigue of structural elements are considered. A comparative analysis of numerical results with experimental data was carried out. The efficiency of the model for describing the process of thermal fatigue of materials and structures under multiaxial disproportionate paths of thermal cyclic loading has been confirmed.